Evaluation of Ore Deposits Potential in the Andahuaylas

MINERAL RESOURCES AND ENERGETIC DIRECTION
METALLOGENY PROGRAM
GE-24 PROJECT
“Evaluation of Ore Deposits Potential
in the Andahuaylas – Yauri Batholith”
Malachite occurrences (Morosayhuasi cluster)
EXTENDED ABSTRACT
TECHNICAL SCIENTIFIC REPORT
Prepared by
Raymond RIVERA, Alberto BUSTAMANTE, Jorge ACOSTA y Alex SANTISTEBAN
Lima – Perú
November, 2010
Content
Abstract
Introduction
1.- General Outlines
1.1 Study zone location
1.2 Accessibility
1.3 Antecedent
1.4 Work methodology
2.- Regional Geology
2.1 Regional stratigraphy
2.2 Intrusive rocks
3.- Economic Geology
3.1 Angostura
3.2 Santa Rosa de Virando
3.3 Atacancha
3.4 Yuringa
3.5 San Diego
3.6 Lahuani
3.7 Jara – Jara
3.8 Utupara
3.9 Alrededores de las bambas
4.- Regional Geochemical (stream Sediment)
Introduction
4.1 Regional Petrogenetic Domain interpreted by stream sediment
4.2 Geochemical of stream sediment in Andahuaylas – Yauri Battholith
4.3 Geochemical of stream sediment in the Colca and Jalaoca – zones
5.- Isotopic and Geocrhonology data interpretation in the Andahuaylas –
Yauri Batholith
Introduction
5.1 Interpretation of isotope data
5.2 Location of the study area within the Pb isotopic provinces in the Andes (Macferlane
et al., 1990)
5.3 Pb - Pb isotopic compositions of some deposits in Peru.
5.4 Pb - Pb Isotopic comparison of the Batolito Andahuaylas – Yauri porphyries vs
Chilean porphyries.
6.- Conclusion
ABSTRACT
INGEMMET through its Resources Mineral and Energy Direction – Metallogenic Program, signed
an international cooperation agreement with the Korean Geological Survey (KIGAM) with the
purpose of evaluating the ore deposits potential in the Andahuaylas – Yauri Batholith. This
investigation includes
metallogenetic interpretations using
geochronological, isotopic,
petromineralogy, structural studies, as well as geochemistry of rocks and sediments.
The importance of this area has increased over the years, during which many exploration works
were carried out and consequently, many mineral occurrences have been discovered.
Considered now as a probable extension of some copper belts of Chile (Perelló et al., 2003);
nearly 70% of the area has been granted as mining concessions to different mining companies.
Initially, this was considered exclusively a Fe-rich zone, but later on more detailed studies came
to the conclusion that it hosts a series of ore deposits related to Cu – Au – Mo porphyry systems.
The international cooperation project lasted approximately 9 months, and included three field
trips. During this period, mines, projects, prospects and potential areas free from mining claims
were evaluated. The Andahuaylas - Batholith domain was divided into two study subzones,
known as “A” and “B”. One of the main areas in the subzone “A” was Cotabambas, where a
series of porphyry deposits are located and are known collectively as the Cotabamba cluster. In
the surroundings of this cluster, the Colca area was recognized, which has some potential to host
an ore deposit. The geologic features are very similar to those of the Cotabambas cluster and
small outcrops of malachite along fractures can be observed.
Several mineral occurrences were visited in zone B, such as: Angostura, Santa Rosa de Virundo,
Yuringa, Atacancha, San Diego, Lahuahi, Jara Jara, Utupara and the surrounding areas of Las
Bambas. Within this subzone, the Jalaoca area was recognized as an important potential area.
This is located about 8 Km west from the Mollebamba city, very close to the inactive mines of San
Diego and Lahuani. Polymetallic vein-type mineralization (quartz – molybdenite – hematite –
chalcopyrite – bornite and galena) has been identified, as well as stockwork structures with piryte
and chalcopyrite probable related to porphyry deposits.
Another interesting area in the subzone “B” was Supamarca. This occurrence is located on the
left side of the Abancay – Andahuaylas road. Copper suphide mineralization and hematite in thin
laminates associated with siliciclastic rocks such as the sandstones of Muñani Formation (Upper
Cretaceous – Paleocene) have been identified. These occurrences share some common features
with such copper occurrences in red beds in the eastern sector of the Andahuaylas – Yauri
Batholith.
This document presents new geochemical interpretations based on geochemical analysis of
rocks and stream sediments. Geochemical graphic representation of major and trace elements
give us an idea about the type of magmatism developed in the area and its associated potential.
Isovaloric maps of stream sediments confirm the potential that some areas.
Interpretation of the data that polished and thin sections offer, confirm the type of rock and
magmatism in the area of study. Finally, using the isotopic data collected from different studies it
related the isotopic signatures with the expected tonnage for some porphyry deposits.
In this investigation, samples were collected from the Cotabambas cluster for isotopic and
geochronology studies. Those samples are being currently analyzed at KIGAM laboratories
(Korea).
This INGEMMET and KIGAM joint work tries to gather all the information related to the
Andahuaylas – Yauri Batholith, and to update the existing geological data with the new data
obtained from the field and office work, with the final purpose of providing exploration companies
a new regional tool that will help them to better conduct their exploration campaigns.
INTRODUCTION
The origin and evolution of mineral deposits in Peru are related to a series of magmatic events,
many of them are associated to subduction processes that take place in the Peru-Chile trench.
One important pulse of this magmatic activity is represented by the voluminous intrusive rocks
that comprise the Andahuaylas-Yauri batholith.
Important research has been conducted in this batholithic domain, Perelló et al., (2003, 2004),
Carlier et al., (1989), Bonhomme & Carlier (1990) stand out among them.
The general
conclusion of all these investigations highlights the great potential of the Andahuaylas-Yauri
batholith.
This belt is located between the Western Cordillera and the Altiplano of the Ayacucho, Cusco and
Puno regions. The belt is bounded on the north by a regional structure known as the Abancay
deflection, and on the east by the Urcos-Sicuani-Ayaviri fault system (Carlotto, 1998). The
structural controls of the southern and western parts are difficult to interpret because the Miocene
volcanic cover hides any pre-Miocene structural feature. These faults are thought to have been
the boundaries of a tecto-sedimentary basin that controlled the Mesozoic sedimentation,
generally composed of limestone (Albian–Turonian Ferrobamba Formation), and siliciclastic rocks
(Jurassic–Cretaceous Yura Formation, and the Altiplano Mara Formation). (Perelló et al., 2003).
More than two dozen mining districts are located to the west, south and southwest of Cusco,
defining an elongated province that extends over 300 km from Andahuaylas in the NW to the SE
in Yauri, covering an approximate area of 25 000 square km. (Bellido & DeMontreuil, 1972).
From a geological point of view, the intrusive rocks have the greatest economic potential.
Commonly known as the Andahuaylas-Yauri batholith (Carlier et al., 1989; Bonhomme y Carlier,
1990), moderately differentiated, these rocks have shown a strong affiliation with porphyry Cu-AuMo, skarn Fe-Cu deposits (Perelló et al., 2003), and Au veins in sedimentary rocks. Spatial and
temporal correlations suggest that the batholith is related to mineral occurrences, with ages
ranging from 48 to 30 m.y. (Carlotto, 1998)
A number of mineral occurrences have been recognized in this sector, but for a better
understanding, they have been named in groups or clusters, which contain more than one ore
deposit with geological features that indicate that they are closely interrelated. For example:
Tintaya Cluster (Tintaya, Quechua and Antapaccay), Katanga (Katanga, Monte Rojo and San
José), Las Bambas Sulfobamba, Querobamba, and Chalcobamba), Cotabambas (Azullccaca,
Ccalla, Huaccle, and Ccarayoc), and finally Morosahuas cluster (Llocllacsa, Cha-Cha, Quenco,
Chicaccasa) (Perelló et al. 2003). All the abovementioned deposits are located in the eastern
part of the Andahuaylas-Yauri batholiths. However, the presence of many occurrences is also
known in the western part, such as Angostura, Trapiche, Utupara, Santa Rosa de Virando,
Lahuani, Antilla, San Diego, Yuringa, Jara – Jara, Leonor, Los Chancas, Haquira, Cristo de los
Andes, etc. The presence of many small gold vein occurrences associated with limestone must
be stand out, which are currently being worked artisanally.
This belt is currently considered as an extension of the Chile Eocene-Oligocene Belt, where
important porphyry-type deposits can be found. The initial strontium isotopic ratios indicate that
the Andahuaylas-Yauri batholith porphyry are of moderate to low tonnage (Bustamante, 2008).
The contribution of this research is that it presents new geochemical, geochronological, isotopic,
and petromineralogical interpretations, which will help to better understand the metallogeny of the
area. It also presents updated information of different mineral occurrences that strengthen the
economic geology of the area, thus being very useful for prospectors as an updated guide for
explorations.
1. - GENERAL OUTLINES
1.1 Study zone location
This study area is in the Western Cordillera of the Ayacucho, Apurimac, Cusco, and
Arequipa regions.
It includes 12 quadrangles (1:100,000 scale) approximately,
comprising the provinces of Sucre and Anta in Ayacucho; Antabamba and Andahuaylas
in Apurimac; Urubamba and Chumbivilcas in Cusco; Espinar and La Unión in Arequipa
(Fig. 01). The study area is delimitated by the following coordinates:
13º 00’ 00” – 15º 00’ 00” LS
74º 00’ 00” – 71º 00’ 00” LW
The Andahuaylas-Yauri belt covers and area of approximately 25 000 square km, and is
located at a distance of approximately 300 km from the Peru-Chile trench. This area has
one of the strongest Andean orogeny sialic crusts (50 to 70 km; James, 1971) and it is
located in the transition zone between a normal subduction regimen between southern
Peru and northern Chile, and a flat subduction zone in the central and northern Peru
(Cahill and Isacks, 1992). It is located immediately southeast of the Abancay deflection
(Marocco, 1978). Metallogenetically, the Andahuaylas batholith is within the main arc
domain (Clark et al., 1990), and within the XV belt, named Porphyry-skarn Cu-Mo (Au,
Zn), and Au-Cu-Fe deposits, related to the Eocene-Oligocene intrusive (INGEMMET,
2009). The region includes the area of the intermountain depression between east and
west of the Cordilleras, and the northernmost area of the Altiplano (Carlier et al., 1996;
Chavéz et al., 1996).
The western part of the belt is characterized by a steep
mountainous topography, where snow-capped mountains ranges are above the 4500 and
are cut by 2000m-deep canyons. These canyons are the main drainage system in the
región and include the Santo Tomas, Urubamba, Apurimac, Vilcanota, Mollebamba, and
Antabamba rivers. All these drains are directed towards the Amazon basin. The eastern
and southern part of the region is characterized by a gently topographic undulation of a
platform (approx 4000 m) that extends into the Bolivia altiplano.
Figure 1.1
1.2 Accessibility
The main and fastest way to Access the study area is by air, departing fom the “Jorge
Chavez” International Airport (Lima), and landing in the “Velasco Astete” Airport (Cusco).
The flight lasts approximately 1 hour and 15 minutes. Another route of the flight would be
from Lima (“Jorge Chavez” Airport) to Juliaca (“Manco Capac” Airport). The flight lasts
approximately 1 hour and 45 minutes, and from Juliaca to the city of Cusco it takes
approximately 5 hours on a paved road.
From Cusco to the small towns within the region the access routes are generally gravel
roads and sometimes unpaved roads.
Some of the main gravel roads are:

Cusco – Abancay – Andahuaylas

Lima – La Oroya – Huancayo – Ayacucho – Andahualylas

Nazca – Puquio – Andahuaylas.
1.3 Antecedent
Until the late 80’s limited geological research had been conducted in the AndahuaylasYauri belt, and it was primarily known for its Cu magnetite skarn deposits (Terrones,
1985; Bellido et al., 1972; Sillitoe 1976, 1990; Santa Cruz et al., 1979; Enauidi et al.,
1981; Aizawa y Tomizawa, 1986),
These occurrences were considered by many researchers as copper skarn associated
with sterile intrusions (e.g. Einauide et al., 1981; Noble et al., 1984), although the
potassic alteration in porphyry stocks hosts have been described and characterized as
such (Yoshikawa et al., 1976; Noble et al., 1984). At the end of the 80’s a complementary
regional work of detailed geological studies in Tintaya and Katanga (Carlier et al., 1989),
followed by an intensive grass-roots exploration in the region during the 90’s, proved the
alteration and mineralization styles, which are typical of the porphyry systems (e.g. Fierro
et al., 1997), and resulted in the discovery of additional porphyry Cu with economic
potential, such as Antapacay (Jones et al., 2000), Los Chancas (Corrales, 2001), and
Cotabambas (Perelló et al., 2002), as well as porphyry-skarn mineralization in
Coroccohuayco (BHP Company Limited, 1999). Zinc-rich Mississippi Valley-type
mineralization was also found in the region (Carman et al., 2000) adding these to the
metallogenetic diversity of the belt.
There are numerous geological reports and articles prepared by different mining
companies operating within the study area, and among them we can mention those made
in the Trapiche mineral deposit, Utupara,Cotabambas, etc. Among the regional studies
we can mention that of Perello et al. (2003) ”Porphyry-Style Alteration and Mineralization
of the Middle Eocene to Early Oligocene Andahuaylas-Yauri Belt, Cuzco Region, Peru”,
as well as regional work conducted by INGEMMET which has been published, such as
the bulletins of the National Geological Chart – Series A
1.4 Work Methodology
It must be emphasized that the work methodology was conducted based on a regional
scale (scale of 1:300 000) including 100% of the Andahuaylas batholith outcrops. The
development of the entire project encompasses three major stages.
The first phase known as the office work I, is characterized by an extensive compilation
of technical and scientific information, which is synthesized and screened in geological
folios using
version 9.3 of Arc GIS software. All this information makes it possible the assessment of
the area from different points of view combining geochemical, structural,
geochronological, and isotopic information. In addition, each of these folios has different
geological value depending on the reliability of the information that has been projected
onto them
The second stage is considered by some geologists as the most important one, and it
has direct relation with the field stage. This stage was conducted in three field trips, 21
days each. During this period main deposits of the Andahuaylas batholith were visited.
The purpose of the field trips was to check and take an inventory of the occurrences
reported in previous works, and to take rock samples of the visited deposits, as well as to
describe the main field characteristics that will allow us to compare or establish the
differences between them.
The last stage is known as the office work stage II. During this stage the samples
collected in the field are sent to the laboratory for their respective geochemical analysis
(Atomic absorption, XRF, ICP-MS, etc.). Polished and thin sections of the samples
previously selected are also examined. Upon receiving the geochemical results, these
are interpreted and the folios are updated with the new data. Cross-checking all the
geological information, we try to find some new relations that allow us to have better
exploration guidelines, as well as to try to understand the genesis of the different types of
mineral deposits in our study area.
2.- GEOLOGIC SETTING
The geology of the region is dominated by a set of Cenozoic plutons named Andahuaylas – Yauri
Batholith (Carlotto, 1988) which intrude the Mesozoic marine sedimentary sequence that consists
of clastic rocks of the Yura Group (Jurassic), carbonate horizons of Ferrobamba Formation
(Cretaceous) and to a lesser extent dominantly lacustrine sedimentary rock of the Chilca and
Quilque formations (Paleocene - Eocene).To the north the geology is mainly dominated by
several volcanic sequences and volcanic - sedimentary (Anta Formation, middle Eocene – lower
Oligocene) and continental sedimentary rocks including the "red beds" series of the San
Jerónimo Group (Lower Eocene-lower Oligocene; Carlotto et al., 2000).
2.1 Regional Stratigraphy
In the study area, the oldest rocks are Precambrian gneisses that found northwest of
Cusco (Carlotto, 1998), then we have a Paleozoic sequence (Cambrian-Lower Permian)
of more than 10 000 m thick constituted by volcanosedimentary, marine and continental
sequences (Marocco, 1978; Carlotto et al., 1996a; Carlotto et al., 1997). At the top of the
pre-Andean basement lie volcanic and clastic rocks sequences of the Mitu Group
(Permian-lower Triassic), with over 1000 m in thickness. During the Mesozoic and
Cenozoic the sedimentation is mostly Jurassic and Cretaceous and was developed in two
main basins, the West Basin or also named the Arequipa Basin (Vicente et al., 1982) and
the Eastern Basin or also named the Putina Basin (Jaillard, 1994), these basins were
separated by a structural high called Cusco-Puno which includes about 900 m of red
beds interbedded with shale, limestone and gypsum (Carlotto et al., 1993; Jaillard et al.,
1994). Arequipa Basin becomes the Western Cordillera, and consists of a sedimentary
sequence of about 4 500 m thick.
Putina Basin is a Upper Cretaceous sedimentary sequence that consists of marine clastic
and carbonate rocks, with a thickness of about 2 600m (Jaillard et al., 1993, Jaillard,
1994, Cardenas et al., 1997).
From Eocene to Lower Oligocene in the study area basically there are two stratigraphic
units: The San Jerónimo Group and Anta Formation.
Fig. 2.1.- Regional stratigraphic columns (Carlotto et al., 1996, 1999).
San Jerónimo Group is constituted by Kayra and Soncco formations, consisting of a red
beds sequence of 4 500m thick composed of sandstone, shale and volcanic
microconglomerates, the San Jerónimo Group has been dated in the upper tuffs horizons
of the Soncco Formation by K-Ar giving age of 29.9 ± 1.4 Ma and by Ar-Ar with 30.84 ±
0.83 Ma (Carlotto, 1998, Fornari et al., 2002). Between Cusco and Sicuani in the Soncco
formation basal sandstone there are mineralized horizons of Cu stratiform with chalcocite
hypogene, bornite and supergene cupper oxides (Cardenas et al., 1999) and show some
similarities to the Red Beds deposits of the Bolivian Altiplano (eg, Corocoro, Sillitoe,
1989) and northern Chile (San Bartolo, Travisany, 1979). The San Jerónimo Group is the
equivalent of the Puno Group in the peruvian Altiplano. Anta Formation is a volcanic
sequence of about 1 000 m in thickness, this sequence has been dated to the southwest
of Cuzco in two biotite-rich dacitic flows, the first from the middle of the formation by the
method of K-Ar giving ages of 38.4 ± 1.5 and 37.9 ± 1.4 Ma, and the second from
basaltic horizon at the top of the unit dated by K-Ar method giving an age of 29.9 ± 1.1
Ma.
During the upper Oligocene to Miocene was developed a siliciclastic sedimentation
represented by the Punacancha formation with 1500 - 5000 m thick, and the Paruro
formation with more than 1100 m thick. (Perello et al., 2003), in the region also there are
volcanic rocks generally calc-alkaline composition in the sequences of the Cordillera
Occidental (Inner - Cordillera Occidental of Sandeman et al., 1995) and the Altiplano,
which includes the Sillapaca and Tacaza Groups. The Tacaza Group is dominated by
trachyandesites, andesite and rhyolite tuff (Klinck et al., 1986; Wasteneys, 1990; Carlotto,
1998) with shoshonitic rocks in the Santa Lucia area, to southeast of Yauri, and were
dated around 32 and 24 Ma (Clark et al., 1990; Sanderman et al., 1995).
2.2 Intrusive Rocks
The magmatism is represented by multiple intrusive bodies that regionally belong to
Andahuaylas - Yauri Batholith. These rocks outcrop in a belt of NW-SE direction parallel
to the andean region direction between the towns of Andahuaylas in the northwest and
Yauri in the southeast, with an approximate length of 300 kilometers and a width varying
between 10 and 60 kilometers
(Marocco, 1977; Bonhome and Carlier, 1990;
Carlotto, 1998). The westernmost outcrops constitute the bulk of the batholith (bodies up
to 70 km in diameter), while southeast this unit appears as a string of minor bodies, about
10 km in diameter.
The batholith is composed of several intrusive units that tend to focus on two major
groups: a group of diorite and quartzdiorita which constitutes 80% of the batholith and a
smaller group composed of granodiorite, diorite and dacite minor stocks and microdiorita
dikes. Field work generally indicate that the facies of the first group are older, which has
been confirmed by geochronological dating (Carlotto, 1998).
Middle Eocene – Lower Oligocene plutonism (~ 48–30 Ma)
Intrusive rocks this year old are referred to Andahuaylas-Yauri Batholith (Carlier et al.,
1989; Bonhohomme and Carlier, 1990), The outcrops of the batholith have a
northwestern direction and are located at the northeastern edge of the Cordillera
Occidental. The emplacement of the batholith occurred in two main stages (Perello at al.,
2003).
In the early stage occurred intrusions of gabbro, olivine gabbro, gabbro-diorite and diorite
(Carlier et al. 1989, 1996), exposed mainly along the northern edge of the batholith
between Curahuasi and Limatambo (Carlier et al., 1989; Ligardes et al., 1993). Through
petrographic studies were determined that these rocks are typical calc-alkaline facies that
crystallize in the base of the shallow magma chambers, with emplacement temperatures
around 1000º C and pressures between 2 and 3 Kbar.
During the intermediate stage were emplaced rocks with intermediate composition such
as monzodiorites, quartzdiorite, granodiorite and quartz monzodiorites (Carlier et al.,
1989; Bonhomme and Carlier 1990; Carlotto, 1998) which are distributed throughout the
region constituting the main part of the batholith.
Upper Oligocene plutonism (~ 29–26 Ma)
The intrusive activity correspond a series of small syenites stocks with an age of about 28
Ma in the area of Curahuasi (Carlotto, 1998). These intrusions are part of a large
magmatic province that also includes basanites, trachytes, phonotefrites in the Ayaviri
region, with dated ages between 29 - 26 Ma (Carlier et al., 1996, 2000).
3.- ECONOMIC GEOLOGY
INTRODUCTION
This report contains geological information obtained in the field conducted to study the
prospective areas and inactive mines belonging to Andahuaylas-Yauri Batholith. The work was
performed under the agreement between KIGAM and INGEMMET to study the economic
potential of Batholith Andahuaylas – Yauri (Fig. 3.1)
Inactives mines visited were: Angostura, Santa Rosa de Virundo, Yuringa, Atacancha, Yuringa,
San Diego, Lahuani and Jara Jara. It also visited the Utupara exploration prospect and the
surrounding Las Bambas.
The mineralization and alteration in most inactive mines are mainly related to structures (veins)
with economic content of gold, silver and copper. Most of these structures are associated with the
presence of iron and manganese oxides (Santa Rosa, Angostura, and Atacancha Yuringa). In
San Diego the style of mineralization is characterized by polymetallic veins that contain bornite,
chalcopyrite and molybdenite. Lahuani area near San Diego is characterized by alterations, veins
quartz and disseminated mineralization of porphyry Cu. Utupara is a porphyry complex that
includes mineralization porphyritic filoneano type, skarn and porphyritic.
Figure 3.1: Location Map of inactive mines visited
VISETED AREAS
3.1.- Angostura
Location: The area is located in the district of Curpahuasi, province of Apurimac,
department of Grau to 4.7 km northwest of Vilcabamba city. Has the following central
coordinates 753924E, 8445927N and 3527 meters of altitude. (Fig. 3.2)
Figure 3.2: Angostura location Map
Geology
Lithology
In the outcrop area the following types of rocks:

Diorite: that is characterized by light gray, medium-grained texture phaneritic,
plagioclase phenocrysts <3mm in 70%, 10% hornblende, quartz subordinate
<3%.

Limestone: Displays color gray, fine-textured, incipient recrystallization, calcite
veins millimeter. The strata are largely folded.

Marble: white to light gray color with characteristic recrystallization of calcite,
coarse texture. Is restricted to the contacts of limestone with iron oxide
structures.
Structural
The area is dominated by three structural systems whose orientations are N80E/80NW,
N35E/55SE and N30E/85NW. The structures of iron oxides and breccias related to the
mineralization appear to follow the course N70-80E/80NW.
Alterations
The alterations identified in this area are not very extensive and are restricted to the
contact between the dioritic intrusive and limestone producing a marmolization. Also
brecciated structures with iron oxides produce a weak silicification.

Marbled zone: Produced by the recrystallization of the limestones from
metasomatism generated by contact between the intrusive diorite and limestone.
The marble is characterized by its whitish, coarse-textured and is associated with
calc silicate minerals such as wollastonite.

Silicification: is weak and is related to the brecciated structures with iron
oxides. You can identify a silica veining in the contact area.

Propylitization: Weak to moderate affecting the diorite intrusive. It is
characterized by the presence of chlorite and epidote which are replacing mafic
minerals such as hornblende.
Mineralization
The main mineralization is associated with brecciated structures (shear zones) in the
limestone whose orientation is N70-80E. These structures are associated with the
presence of iron oxides, manganese oxides and so subject to silica, pyrite and
chalcopyrite. The principal metal extracted is gold and this is associated with Fe and Mn
oxides such as limonite, hematite, magnetite and pyrolusite.
Discussion:
The mineralized structures correspond to tectonic breccias are affecting marbled
limestone and in turn are in contact with the intrusives. It is possible that the
mineralization was deposited along the axis of an anticlinal flank very closed. The
economic potential of the area is defined for gold mineralization which is hosted in these
structures.
Photo 3.1: Marbled limestone outcrop cut by structures of iron oxides. Note the mining work on the road
Photo 3.2: Diorite outcrop cut by felsic veinlets
Photo 3.3: Structure of hematite-goethite-limonite, pyrolusite of marbled limestone cutting direction
N70W. Note the mining work.
Photo 3.4: Area of contact between intrusive diorite and limestone marbled.
3.2 SANTA ROSA DE VIRUNDO
Location
The Virundo Santa Rosa mine is located in the district of Turpay, Grau province and
Apurimac department, to 19 km southwest of the Vilcabamba city. The central
coordinates are 751783E 8423436N and 4018 meters of altitude. (Fig. 3.3)
Figure 3.3: Santa Rosa location Map
Geology
Lithology
The area is dominated by limestone, to a lesser extent are intrusive and pyroclastic
rocks.

Limestone: They are gray to dark gray color, fine texture micrite, with millimetric
veinlets of calcite. In some areas these limestones are brecciated by faulting.

Dacite porphyry: light gray-colored stock with crystals of plagioclase and
potassium feldspar <5mm. Fine matrix of plagioclase with hornblende <3mmm
subordinate quartz and <3%. The rock is moderately propilitizada and
weathered.

Lapilli tuff: white color, polymictic fragments, matrix rhyodacitic. The rock is
mostly obliterated by the texture change.

Marble: white to light gray coloration, recrystallization of calcite, coarse texture.
Is restricted to the contacts of limestone with iron oxide structures.
Structural
The area is dominated by three structural systems whose orientations are N70E/55NW,
N20E/70SE, N60W/85NE. The structures of iron oxides and breccias related to
mineralization are the direction N70-80E.
Alterations

Silicification: is weak and is affected mainly the lapillítica tuff. In some areas is
associated with kaolin

Argilization: Subsequent to the Toba lapillítica, kaolin minerals is replacing the
matrix and obliterating the original rock texture.

Marbled zone: produced by recrystallization of the limestones from
metasomatism generated by contact with dacite porphyry. The marble is
characterized as gray-colored gray-white, coarse to medium and associated with
calc silicate minerals such as wollastonite.
Mineralization
The mineralization is associated with structures of N70-80E due to iron oxides (hematite,
goethite, limonite) manganese oxides (pyrolusite), jarosite, pyrite, chalcopyrite and
galena subordinate. It is also common fractures found in copper oxides malachite and
azurite.
Discussion
The mineralized structures consist of brecciated shear zones affecting the limestone. The
mineralization is predominantly gold in sulfides (pyrite) that have been oxidized and
leached. It is common to identify iron and manganese oxides rich in gold and silver. In a
smaller proportion are copper oxides (malachite and azurite). The potential of the area is
defined for structures (breccias) with gold and silver
Photo 3.5: brecciated structure with oxides of manganese and iron oxides, hematite-goethite, limonite,
pyrolusite and marbled limestone cutting direction N70W. Note the mining work.
Photo 3.6: Structure subvertical with manganese oxides and iron oxides in limestone marbled.
Photo 3.7: brecciated structure with oxides of manganese and iron oxides hematite-goethite-limonite.
Direction N70W. Esperanza pit.
Photo 3.8: Units dendritic pyrolusite coating fractures in marble.
3.3 ATACANCHA
Location
It is located in the district of Curpahuasi, Grau province, Apurimac department, 10 km
NW of the Vilcabamba city . The central coordinates are 748887E, 8447800N and 4318
meters of altitude. (Fig. 3.4)
Figure 3.4: Atacancha location Map
Geology
Lithology
In the outcrop area limestone, diorite and marble.

Limestone: outcrops of gray to dark gray color, fine texture, micritic, with
millimetric veinlets of calcite. In areas is partly brecciated by faulting. It is
common to have sigmoid veins and fractures filled by calcite.

Diorite: This intrusive is characterized by a light gray color, the texture is
medium grain phaneritic predominantly plagioclase <5mm, hornblende <3mm.

Marble: It is characterized by gray to white colors in some cases you can identify
layering, coarse texture is characterized by recrystallization of calcite.
Structural
The area is dominated by three main structural systems whose orientations are
N55W/55SW, N20E/83NW, N50W/80NW. The structures of iron oxides and breccias
related to mineralization N55W/55SW remain on course. Failures have been identified
course of conduct which have a dextral direction N20-25E.
Alterations

Marbled zone: Produced by recrystallization of the limestones from
metasomatism generated by contact with the diorite intrusive. The marble is
characterized as gray-colored gray-white, thick texture is medium and is
associated with calc silicate minerals.

Silicification: Your presence is limited to structures, is weak and appears to
affect the contact areas with limestone and diorite.

Calc-silicates: It occurs due to contact between the limestone structures. Is
prograde with minerals such as pyroxene and calcite.
Mineralization
The mineralization is associated with N55W/55SW course structures with iron oxides
(hematite, goethite, limonite) and sulfides related to the presence of Au and Ag have a
weak silicification related to the presence of calc silicate minerals such as pyroxene and
partners the presence of sulphides such as pyrite and chalcopyrite in cubic crystals
Discussion:
The mineralization is mainly related to the presence of structures of N50-60W
characterized by the presence of iron oxides and a subordinate sulfides (pyrite,
chalcopyrite), suggesting that these structures were initially composed of sulfides and
quartz and a lesser proportion which were subsequently been oxidized and leached in
many cases leaving boxwork type textures with iron oxides. The potential in this area is
defined for veins with Au and Ag
Photo 3.9: brecciated structure with iron oxides hematite-goethite-limonite N55W course cutting
limestone.
Photo 3.10: Area of contact between diorite with limestone in the presence of pyroxene-calcite and pyrite.
Photo 3.11: Structure with iron oxides hematite-goethite-limonite N55W course cutting limestone. Informal
mining work.
Photo 3.12: Area of contact between diorite and limestone with pyrite and chalcopyrite with pyroxenecalcite
4.-YURINGA
4.1. Location:
The area is located in the district of Curpahuasi, province of Apurimac, Grau department
to 11 km NW of the city of Vilcabamba. Its central coordinates 747264E, 8448029N and
an altitude of 4434 meters. (Fig. 3.5)
Figure 3.5: Yuringa location Map
Geology
Lithology
Limestone outcrop in the area, diorites, tonalites and marble.
Limestone, outcrops of gray to dark gray color, fine texture, micrite with veins of calcite.
In zone is brecciated by faulting. It is common to have sigmoid veins and fractures filled
by calcite.

Diorite: This pluton is characterized by a light gray color, the texture is medium
grain phaneritic predominantly plagioclase <5mm, hornblende <3mm.

Tonalite: light gray, medium-grained texture phaneritic. They are as essential
minerals to plagioclase (50%) and quartz (15%) with grain sizes smaller than
5mm. It has also been identified subordinate hornblende and feldspar.

Marble: It is characterized by gray to white colors in some cases can be seen
banded texture, thick texture is characterized by recrystallization of calcite.
Structural
There are three main system whose directions are: N70E/40NW, N10E/65SE,
N25E/58SE faulting has been identified direction of N25E oriented dextral and normal
faulting oriented N10E and N75E. The veins follow the following guidance N70E/40NW.
Alterations

Marbled zone: Produced by the contact between limestone and intrusive diorite
and tonalite. The marble is characterized as gray-colored gray-white, coarse to
medium.

Silicification: Is restricted to the veins, is of moderate intensity appears to affect
the host rocks.
Mineralization
The mineralization is related to veins with silver sulfosalts assemblages associated with
pyrite - barite-siderite. Structures are often brecciated and related fault zones oriented
normal type N70E/40NW. These structures are partially oxidized generating presence of
iron oxides such as goethite, limonite, jarosite. Can also be identified as chrysocolla
copper oxides.
Discussion
The veins are related to normal faults N70E orientation is characteristic of these the
presence of silver sulfosalts (pyrargyrite) mineral typical low-temperature hydrothermal
environments and related to the presence of barite (high) which would indicate that these
veins would the tops of the highest levels of the system. The presence of gold is subject
so does the copper oxides.
Photo 3.13: Yuringa mine of intrusive rocks (tonalite). Note the fracture rate associated with normal
faults. Informal mining work.
Photo 3.14: Structure sigmoid in dextral fault zone associated with vein with barite and calcite.
Photo 3.15: dextral fault plane. Note the kinematic structures indicating the direction of motion. Inside
the mine.
Photo 3.16: Display of hand vein. Silver sulfosalts crystals intergrown with barite and associated with
iron oxides.
5.- SAN DIEGO
Location
The area is located in the district of Juan Espinoza Medrano, province of Apurimac
department Antabamba 8 km SW of the city of Mollebamba. Its central coordinates
717370E, 8399270N and an altitude of 4606 meters. (Fig. 3.6)
Figure 3.6: San Diego location Map
Geology
Lithology

Limestone: dark gray-colored outcrops, fine texture micrite with veins of calcite.
In zone is brecciated by faulting.

Monzogranite: Intrusive characterized by a gray with pink hue. The texture is
medium grain phaneritic. Minerals predominate as plagioclase (<2 mm), feldspar
(<3mm) and quartz to a lesser extent. Hornblende, biotite and magnetite as
accessory minerals.

Diorite: This intrusive is characterized by a light gray color, the texture is
medium grain phaneritic, essential minerals are plagioclase <3mm and
subordinate feldspar. The main accessory mineral is hornblende.

Marble: It has gray to dark gray color, is caused by the metasomatism occurred
between the intrusive diorite and monzogranite with limestone. The degree of
recrystallization is moderate
Structural
We have identified three main systems whose directions are 70E/70SE, NS/60E,
N60W/45SW. The veins are controlled by the system N70-80E 60-70 tilt to the SE. Has
been identified dextral faulting with NS and normal faulting N80E direction.
Also faulting also occurs due to N25E oriented dextral and normal faulting oriented N10E
and N75E. The veins follow the guidance N70E/40NW.
Alterations

Silicification: is related to the presence of veins which moderately altered host
rock to produce a replacement of silica minerals in the intrusive diorite. This
silicification is local and is restricted to halos of the grain.

Calc-silicates: There are two types of alteration type calc-silicates with prograde
and retrograde assemblages. These changes are related to the contact between
the intrusive diorite with limestone also to the presence of the grain.

Prograde: Characterized by the assemblage garnet-pyroxene
Retrograde: Mainly actinolite-chlorite, amphiboles are replacing pyroxenes.
Mineralization
The mineralization is controlled by grain direction N70E dipping 70SE, filling textures are
being able to identify the following assemblages:
1st event: quartz-molybdenite + chalcopyrite + pyrite
2nd event: hematite (specular)
3rd event: chalcopyrite-pyrite-bornite-calcite
4th event: calcite - quartz crystals, hyaline
Discussion
The presence of at least four mineralization events indicates the existence of multiple
phases in the grain filling the most important from the economic point of view as the third
event that brings significant copper mineralization (chalcopyrite-pyrite-bornite- calcite). It
is also important to mention that these structures generate a halo in their respective host
rock with altered calc-silicates (pyroxene, garnet and actinolite) without mineralization
identified to date.
Photo 3.17: Pit in old work of mine showing fault plane with chalcopyrite, molybdenite and copper
oxides.
Photo 3.18: Old mine.
6.- LAHUANI
Location:
The area is located in the district of Juan Espinoza Medrano, province of Apurimac department
Antabamba 8 km SW of the city of Mollebamba. Its central coordinates 716628E, 8399384N and
an altitude of 4610 meters. (Fig. 3.7)
Figure 3.7: Lahuani location Map
Geology
Lithology

Limestone: characterized by presenting a dark gray color, fine texture with veins
of calcite micrite. It is common to have sigmoid veins and fractures filled by
calcite.

Monzogranite: characterized by intrusive gray with pink hue. The texture is
medium grain phaneritic. Minerals predominate as plagioclase (<2 mm), feldspar
(<3mm) and quartz to a lesser extent. Also hornblende, biotite and magnetite as
accessory minerals.

Granodiorite: This intrusive is characterized by having a light gray color, the
texture is medium grain phaneritic, essential minerals are plagioclase <3mm
feldspar <3mm. and quartz. The main accessory mineral is hornblende.
Structural
The area is dominated by three main systems whose directions are N70E/70SE, NS/60E
and N50W/45SW. These systems have been recognized in the field but can also be
identified at the regional level from the interpretation of satellite images. N70E system is
associated with failure of standard and related to polymetallic veins with chalcopyritebornite-molybdenite-pyrite, as in the San Diego mine. N40-50W system is related to
calcite-galena veins with iron-oxides. NS systems are dominated by fault type associated
with veinlet sinextral and quartz in the monzogranite and granodiorite.
Alterations

Quartz-sericite-pyrite: We present affecting the monzogranite and granodiorite.
Is sericite replacing plagioclase crystals and feldspar in some cases to obliterate
the texture of the rock. The rock matrix has been altered by an intergrowth of
sericite with quartz in the presence of disseminated pyrite.

Silicification: is related to the presence of veins which moderately altered host
rock to produce a replacement of silica in the intrusives. This silicification is local
and is restricted to halos of the grain.

Calc-silicates: These changes are related to contact with the intrusive veins and
limestone. It has identified the following types:
Prograde: Characterized by the assemblage garnet-pyroxene
Retrograde: Mainly actinolite-chlorite, amphiboles are replacing pyroxenes.
Mineralization

Vein type: This first style is related to a structure with calcite-pyrite-galena, these
veins causing the host rock altered calc silicate minerals.

Porphyry type: It has been recognized in the area Lahuani Area. The mineralization
is characterized by the presence of chalcopyrite disseminated in the intrusive rocks
(granodiorites and monzogranite) which are affected by phyllic alteration (quartzsericite-pyrite). Likewise, these intrusive rocks are cut by a series of quartz veinlets
stockwork type arrangement. The quartz veinlets have a potassium feldspar halos
and / or albite. In some cases, these veinlets are associated with pyrite and
chalcopyrite. Magnetite-chalcopyrite veinlets and quartz-chlorite-pyrite have been
identified by cutting the granodiorite in the central part of the area.
6.3. Discussion
The lithology, alteration and mineralization identified in the area of Lahuani suggests that
area is highly prospective for porphyry deposits of Cu and polymetallic veins. Structurally
occur intersection of three structural systems associated with the failure Mollebamba
Regional. These systems are the same that control Trapiche porphyry deposits and
Panchita near the study area. To continue with the prospecting work which should
include a detailed mapping of the area so that you can characterize the lithology,
alteration and mineralization in the area. Also also recommends the collection of rock
samples to define more precisely the geochemistry of the area.
Photo 3.19: Outcrop of granodiorite with phyllic alteration (CZ-ser-py) and type veinlet quartz stockwork.
Photo 3.20: Granodiorite with stringers of magnetite-pyrite-chalcopyrite.
7.- Jara - Jara
Location
The area is located in the district of Lambrama, province of Apurimac, Abancay
department to 1.0 km north of town of the same name. The central coordinates are
742900E, 8462500N and an altitude of 3770 meters. (Fig. 3.8)
Figura 3.8: Jara Jara Location Map
Geology
Lithology

Limestone: dark gray-colored outcroppings, fine texture micrite with veins of
calcite. It is common for these fractures sigmoid veins filled by calcite.

Diorite: This pluton is light gray in color, texture is medium grain phaneritic,
essential minerals are plagioclase <3mm and subordinate feldspar. The main
accessory mineral is hornblende.
Structural
We have identified three main structural systems whose directions are N75E/65SE,
NS/65E, N80E/65SE. The veins are controlled by the system N70-80E 60-70 tilt to the
SE. Has been identified dextral faulting with NS and normal faulting N80E direction.
El área se encuentra localizada en el distrito de Lambrama, provincia de Abancay
departamento de Apurímac a 1.0 km al norte de la localidad del mismo nombre. Tiene
como coordenadas centrales 742900E, 8462500N y una altitud de 3770 msnm.
Alterations

Silicification: It is moderate and is restricted to the host rocks of the veins

Sericitization: Relates to areas of faulting and the boxes of the grain. Affects the
diorite and can identify a replacement of plagioclase by sericite. In some cases
this alteration comes to obliterate the original rock texture.

Propylitization: It is the most abundant and is affecting the diorite. Chlorite is
the major mineral and this is replacing ferromagnesian has also been identified
magnetite and pyrite.
Mineralization
The main style gold vein type mineralization. The veins of gold have economic content
and are characterized by the presence of quartz with subordinate pyrite and chalcopyrite.
The power of the structures is less than 30 cm and these are altered host rocks locally
producing a moderate sericitization and in some cases a weak silicification. The vein
system is controlled by faults oriented N70-80E affecting mainly dioritic rocks.
Discussion
The mineralization is related to structures that cut quartz granodiorite phaneritic texture.
There are many ancient works some of which apparently date back to colonial times. The
potential for this area of quartz veins with gold content
Figure 3.21: sample of quartz
vein associated with pyrite,
subordinate chalcopyrite and
iron oxides
8.- UTUPARA
location
The area is located in the district of Huaquirca, province of Apurimac department
Antabamba 4.5 km east of the city of Antabamba. Its central coordinates 734029E,
8410265N and is at an altitude of 4300 meters. (Fig. 3.9)
Figura 3.9: Utupara Location Map
Geology
Lithology

Biotite lamprophyres: Rock leucocratic colored dark gray to black, consisting of
85% biotite megacrysts up to 8 cm. The crystals are well developed to be easily
peelable, the matrix is sparse and consists of magnetite 10% and 5% feldspar.
Veinlets is cut by centimeter to decimeter of potassium feldspar.

Diorite: Rock melanocratic, gray to dark gray, medium grain holocrystaline,
phaneritic equigranular texture. It is composed of plagioclase crystals
subhedrales size <4 mm and up to 55%, clinopyroxene subhedrales <3 mm 25%
amphibole (hornblende) <4 mm and 15%, biotite 3%, 1% magnetite. It is the
largest rock outcrop in the area.

Porphyritic diorite: Rock melanocratic, dark gray color that is characterized by
well developed prismatic crystals of amphibole (hornblende) <2 cm. up to 25%,
also biotite crystals with sizes up to 1 cm., the matrix is composed of plagioclase
by 60% which is in subhedrales crystals <2 mm. Other minerals identified in the
matrix are 5% magnetite, hornblende and biotite. This is probably the oldest
intrusive rock this area following the field observations which is cut by almost all
other rock types.

Monzonite: leucocratic, colored pink to gray to pink hue, holocrystaline medium
grain texture is equigranular, composed mainly of elongated crystals of
orthoclase <3 mm up to 35%, 45% subhedral plagioclase, mafic minerals are to a
lesser extent and represented by amphibole (hornblende) euhedral crystals of
size <3mm in 10%, biotite 5%, other 5%.

Biotite monzonite porphyry dyke: It has a light gray color with greenish hue, is
characterized by euhedral crystals of orthoclase present <6 cm. and 20% biotite
crystals centimeter of 3 to 5 cm. by 10%. The matrix is characterized by being
composed mainly of plagioclase equigranular subhedral <4 mm., Hornblende in
large crystals <1 cm. magnetite and, less 1%. The biotite crystals are replaced by
epidote by way of nests.

Andesite dike: Is colored gray to dark gray, aphanitic to microporfídica texture,
euhedral plagioclase crystals of size <3 mm. and up to 30%. The matrix consists
of fine-grained plagioclase up to 60%. The mafic elongated crystals are
composed of amphibole (hornblende) <4 mm. up to 5%, biotite subordinate <1%,
2% magnetite.

Felsic dikes: pinkness leucocratic rock composed mainly of feldspar
(orthoclase) holocrystaline coarse. You can identify centimeter of orthoclase
megacrysts. Cutting is so polydirectional diorite.

Porphyritic monzonite dike: leucocratic, gray with pink hue, inequigranular,
porphyritic texture, is composed of euhedral crystals of orthoclase <5mm
subhedrales plagioclase crystals forming mainly the rock matrix <2 mm and
elongated idiomorphic hornblende crystals <3 mm., 3% biotite, magnetite <1%.

Quartzites: Characterized by having more than 95% quartz in its composition,
the quartz grains are recrystallized product of metamorphism. Outcrop mainly in
the hill in banks of course Utupara N 45-70 W and 30-35 are dipping to NE.

Marble: It has light gray, pink, white reaching depending on the degree of
metamorphism. It consists in 95% recrystallized calcite. In many cases you can
identify calcite veinlets subparallel to bedding. They arise mainly east of the
study area and are limestone grading up to as they move away from contact with
the diorite intrusive Utupara.

Breccias

Intrusive breccias
Are characterized by heterometric and polymictic, the pieces may be subrounded
to subangular. When the breccia is clast-supported fragments are subangular
decimetre size and mainly diorite and monzonite, when the breccia is matrix
supported subrounded lithic fragments are the matrix in this case is mainly
composed of plagioclase and biotite which have been altered to sericite, epidote,
chlorite, iron oxides and clays, also identified disseminated pyrite. The main
outcrop is concentrated in the area where evidence puppy at least two major
events of brecciation.

Tectonic Breccia
These breccias have been identified near the area of contact between quartzite
and diorite, are characterized by angular to subangular fragments, monomitic
heterometric and quartzite, these fragments reach centimeter sizes and are
supported by a matrix of iron oxides and manganese.
Structural
Regionally, the study area is located on the southern edge of the deflection of Abancay
(Marocco, R., 1978) and is characterized by the presence of faults and folds oriented
EW, NW-SE that affect the rocks of the Mesozoic and Cenozoic .
Tectonism above the stocks, this is evident because the failure of these anticlines not
manifest in the intrusive rocks. The NNW-SSE compressional efforts originate EW
fracture system that is evident mainly in the Yura Group quartzite that fracture in fault
zones causing tectonic breccia.
Alterations

Early potassic alteration (Bt-mt-FK-py)
Alteration is more exposed surface area and is affecting the bodies of diorite and
diorite porphyry. Secondary biotite is the main mineral is mainly replacing
pyroxene and amphibole. Is associated with magnetite, feldspar and pyrite.
Magnetite and pyrite are characterized by replacing the mafic minerals (pyroxene
and hornblende).

Main potassic alteration (FK-bt-ab-py)
It manifests itself mainly to affect stocks monzonitic, monzodiorites, and the
breccia dioritic intrusive. Has a structural control following fracturing and breccia
zones. When applied to stocks and monzodiorites monzonitic alteration type is
more pervasive, the plagioclase phenocrysts have been partially or completely
replaced by potassium feldspar, the rock matrix has often been completely
obliterated by alteration making it impossible to distinguish their original texture .
When it affects the diorite breccias and the disturbance is manifested by way of
polydirectional veinlets of K-feldspar, biotite, magnetite, pyrite and albite.

Late potassic alteration (FK-ab + py)
This phase is largely controlled by fractures and applies without distinction to any
of the intrusives. The potassium feldspar is associated with albite and they most
commonly occur in veinlets, in other cases by way of patches partially obliterated
the original texture of the rock, pyrite is subordinate and not always present.

Propylitic alteration (Close-ep-cac-py)
It is characterized by over-imposed on the potassic alteration. Chlorites is
replacing the biotite and pyroxene are also associated with calcite veins, pyritecalcite veins and epidote. This association occurs in later stages of the various
stages potassium. Surface is evident in the contact area of the breccia with the
diorite porphyry intrusive at this you can see the replacement of crystals of biotite
by epidote and chlorite.

Alteration sericite (ser-py + cz)
Has been identified in the area of intrusive breccias affecting primarily the matrix
and is associated with chlorite, clay (kaolin) and with varying content of pyrite,
the presence of silica is restricted. Also presented on-imposed on the potassic
alteration that affects the different intrusive phases, in this case we can see a
replacement of potassium feldspar, plagioclase and biotite by sericite.

Argillic alteration
Their presence is quite limited usually related to the host rocks of the structures
has also been identified in the intrusive breccia zone adjacent to the alteration
sericite. It is associated with fracture zones with limonite. It is pervasive and can
identify a replacement of plagioclase by kaolin in many cases leading to
completely obliterate the original rock texture.

Calc-silicate alteration
It manifests itself in the areas of contact between carbonate rocks and the
intrusive Utupara, is controlled by structures and associations have been
identified prograde and retrograde over-imposed often making it difficult to
identify

Prograde (Grn-he-wo)
It is characterized by the presence of anhydrous minerals have been identified
green and brown garnets (andradite and grossular) associated with diopside and
wollastonite. The diopside is formed as a replacement of biotite and hornblende
diorite. Wollastonite has replacement textures and more often filling fractures in
crystals that can reach centimeter sizes.

Retrograde (cur-mt-esc + ca + ab)
Mostly over-imposed on the prograde phase of destruction and is characterized
by the presence of hydrated minerals formed at the expense of anhydrous
minerals prograde stage. Actinolite is formed at the expense of pyroxenes
prograde phase in thin-section petrographic study can identify that this
replacement is partial in some cases there is pyroxene and amphibole found
together..
Mineralization

Intrusive Breccia Zone
Mineralization in the breccia is mainly disseminated and replacement filling pyrite
and chalcopyrite disseminated recognizing both the clasts and matrix in the
breccia and associated with magnetite and hematite. Filling and replacement
mineralization occurs as veinlets of pyrite, chalcopyrite and magnetite.

Skarn Zone
It consists of a series of bodies of magnetite in both elongated and low dip, the
mineralization occurs along these bodies with dissemination of pyrite,
chalcopyrite,
pyrrhotite,
magnetite.
Pyrrhotite-magnetite
association
is
characterized as replacement textures, pyrite and chalcopyrite are found to a
lesser extent so widespread and in some cases in veins. The mineralization is
associated with mineral phase retrograde actinolite, chlorite and albite.

Mantle zone (quartz structure)
The robes are characterized by being placed in the quartzite, associations
minerals are pyrrhotite, pyrite, chalcopyrite and oro.Están associated with iron
oxides. In general, the textures are brecciated and replacement

Vein Zone
They are thinner structures consist of quartz veins with iron oxides, pyrite and
magnetite, the textures are mostly brecciated and show a cavernous
appearance. In other cases the associations polymetallic mineralization is pyrite,
chalcopyrite, galena, iron oxides and manganese. In both cases the host rock is
a diorite which is argilizada and fractured.
Discusión
The porphyritic complex (Cu-Au) is characterized by having a varied lithology, including
clastic and carbonate sequences of Mesozoic age which are intruded by an igneous
polyphase system has evolved from intermediate stages in the pre-mineralization
characterized by bodies diorite to acidic phases of mineralization stage presence and
monzodiorites monzonites. Faults oriented NNW-SSE and NE-SW control alteration and
mineralization. The potassic alteration is dominated with over-taxation of sericite and
propylitic phases. We have identified three main stages of hydrothermal alteration: Stage
I characterized by an early-stage potassium-bt-mt-py + cpy FK, the Stage II is
characterized by a phase assemblage main potassium FK-bt - ab - m - py -cpy and
related to the occurrence of a breccia intrusive intrusions and monzonitic NS, the Stage
III characterized by late-stage potassic assemblage with FK-ab + py, was notorious in this
case the structural control related to smaller structures.
Photo 3.22: Structure of white quartz with sulfides in quartzite. Note the host rock altered to sericite.
Interior Utupara old mine.
Figure 3.23: Breccia magmatic heterolytic and biotitic matrix. Chalcopyrite and pyrite disseminated in
matrix. Feldspar veinlets.
Photo 3.24: Area of oxides in skarn, chrysocolla, malachite. Chapi-Chapi area.
Photo 3.25: monzonite porphyry dike, crystals <10 mm of potassium feldspar. The dam is cutting
magmatic breccia.
9.- Vicinity of LAS BAMBAS
Location
The area is located in the district of Coyllurqui, Cotabambas province of Apurimac
department. The central coordinates are 786670E, 8445440N and an altitude of 4400
meters. (Fig. 3.10).
Figure 3.10: Las Bambas Location Map.
Geology
Lithology

Limestone: dark gray-colored outcroppings, fine texture micrite with veins of
calcite. In zone is brecciated by faulting. It is common for these fractures sigmoid
veins filled by calcite.

Porphyritic monzonite: intrusive characterized by a gray with pink hue. The
texture is porphyritic. Minerals predominate as plagioclase (<5 mm), feldspar (<5
mm) and quartz to a lesser extent. Hornblende biotite and magnetite as
accessory minerals.

Diorite: This pluton is characterized by a light gray color, the texture is medium
grain phaneritic, essential minerals are plagioclase <3mm and subordinate
feldspar. The main accessory mineral is hornblende.

Porphyritic dacite: Stock hypabyssal colored light gray, porphyritic texture with
plagioclase crystals <5 mm, subordinate feldspar and quartz. The matrix is
aphanitic texture.

Marble: Characterized by dark gray to gray color. It is produced by
metasomatism between the intrusive diorite and monzogranite with limestone.
The degree of recrystallization is intense.
Structural
We have identified three structural systems whose directions are N75E/70SE,
N20W/70NE and N25E/70SE. Quartz veinlets halos potassium and copper oxides are
controlled by the system with inclination N70-75E and dip 60-70 SE.
Alterations

Potassic alteration
This phase is largely controlled by fractures (veinlets) and applies without
distinction to any of the intrusives. The potassium feldspar is associated with
quartz and both are presented mostly as halos in quartz veinlets.

Propylitic alteration
Chlorites are replacing the biotite and pyroxene in monzonites and diorites. They
have also been identified in veins with the assemblage quartz-chlorite-magnetite.

Sericite alteration
Affects the intrusive diorite and monzonite. Manifests replacing feldspar and
plagioclase crystals in many cases obliterating the original rock texture.
Mineralization
The identified mineralization is restricted to quartz veins with pyrite and chalcopyrite. In
the diorite you can see veins and veinlets of copper oxide silica in fractures (chrysocolla
and malachite) and iron oxides produced from sulphide (pyrite, chalcopyrite).
Photo 3.26: veins of quartz-magnetite-actinolite alteration in monzonite with phyllic (CZ-ser-py).
Photo 3.27: halo quartz veinlets of K-feldspar in diorite.
4.- REGIONAL GEOCHEMICAL (STREAM SEDIMENT)
Introduction.The regional geochemical work of stream sediment realized by INGEMMET in the 2 and 3 belts
have served as a tool to differentiate geochemical domains and thus associated with possible
petrogenetic domains
In this way was used the regional geochemical of stream sediment as a tool to determine
metallogenic provinces (Rivera, 2010). The objective of this interpretation was to determine
variations in the regional background and associate to possible metallogenic provinces, which
may have different potential for mineralization.
The regional geochemical interpretation by the background controls resulted in the interpretation
of two different metallogenic provinces known as the domain of the internal arc and the main arc
(Clark et al., 1990).
By regional geochemical interpretation can also infer some regional fault systems such as: the
USA fault systems (Urcos - Sichuan - Ayaviri) that behaves as a high structural separating
internal arc domain of the main arc domain (Clark et al., 1990). Other fault systems can also be
inferred, such as Puyentimari and Patumburco that behaves as transform faults associated to
Abancay deflection (Carlotto et al., 2006) (Fig. 4.7).
In conclusion by this new regional interpretation demonstrated the use of regional geochemical as
a tool to differentiate metallogenic provinces and their possible application to exploration.
At the end of this regional interpretation you can see some isovalue maps of the Andahuaylas Yauri Batholith domain (Cu - Au - Mo), overlaid with locations of major mineral occurrences. Local
Isovaloric maps of the Jalaoca and Colca areas also were interpreted (Au - Cu - Mo).
Isovaloric maps were made using data from regional stream sediment by the Geosoft program
(modulo Chimera), using the minimum curvature method, then the method of smoothing and
finally for better contrast was given the appearance of shadows. These isovaloric maps for a
better compare were added shapes of intrusive rocks and regional fault systems, in order to
provide better space correlations (Fig. 4.6).
Also was made 3D isovaloric maps in order to get a better view of the changes in regional
background (Fig. 4.11)
4.1 REGIONAL PETROGENETIC DOMAINS INTERPRETED BY STREAM SEDIMENT
Main Arc Domain.This petrogenetic domain is characterized for has a potential related to the mineralization
of Cu - Au - Mo - Fe ± (Pb - Zn - Ag). Alkalinity vs silica indicate that this domain is
related to a calc-alkaline magmatism with medium to high potassium content, while the
alumina indicate that this domain lies within the metaluminous environment.
Both types of geochemical classifications are related with magmatism in subduction
environment whose magmas were ascending through large regional faults. Some of
these magmas have a little crustal contamination, and other major crustal contamination,
and this can be seen in the potassium content.
In the figures 4.1 and 4.2 can be appreciated as isovaloric maps of calcium and strontium
defined very well the limit of the petrogenetic environments. It is known that strontium is a
member of the alkaline earths of group IIA (Be, Mg, Ca, Sr, Ba and Ra). The ionic radius
of strontium is 1.13 Anstromg, so higher than the calcium (0.99 Anstromg). Strontium is
also a dispersed element that occurs in calcium-containing minerals such as plagioclase,
apatite and calcium carbonates.
Through many petrological studies it is known that in the domain of the internal arc there
are more intrusive rocks with a greater abundance of plagioclase and mafic minerals that
have in their crystal lattices a high concentration of calcium, which can be replaced by
strontium.
Internal Arc Domain.This domain is characterized for have a Sn - W - Mo - U and REE potential. Alumina
graphics classify the internal arc rocks as peraluminous.
On the other side in figures 4.3, 4.4 and 4.5 can be clearly appreciated as the aluminum;
lanthanum and beryllium elements define the domain of the internal arc. This domain
using geochemical studies of rocks is assigned a peraluminous signature, perhaps
related to processes of anatexia or strong crustal contamination.
Then it is clear that the aluminum element defined very well the internal arc domain and
this is because the firm is peraluminous (Al> Na + K + Ca) and corresponds to the
igneous rocks that outcrop in the study area. On the other hand the lanthanum element is
a light rare earth, whose high concentration is related to igneous rocks with moderate to
strong magmatic differentiation (rhyolite or granite), as Macusani tuffs or some facies of
the Carabaya Batholith .
Goldschmidt and Peters (1932) recognized that beryllium could be enriched in the crust,
because beryllium behaves as a lithophile element and has a geochemistry behavior very
similar to aluminum. Nowadays is estimated to crustal an average 3 ppm, which
represents an enrichment of 50 times in relation to the contents of the primitive mantle.
Beryllium can be found in the majority of minerals, including important rock-forming
minerals, with a very regular concentration of up to 10 ppm or even less, rarely exceeding
100 ppm. Then beryllium is an element incompatible in many geological systems.
However, some minerals have reported that incorporate substantial amounts of beryllium.
The principal beryllium mines are related to pegmatites rocks, but there is information of
occurrence of beryllium in rocks not pegmatites related to peraluminous magmatism.
Several examples are given on the origin of uranium deposits and most of them are
related to deposits that occur in environments strongly to weakly peraluminous, for
example: beryllium-enriched rhyolites (Macusani), beryllium- enriched granite (Cordillera
Carabaya and its possible continuity in the Permo - Triassic granites).
This is one of the reasons why beryllium defines very well the contour of the isovaloric
maps of stream sediment in the internal arc domain. Although there are some high
concentrations of beryllium and lanthanum in the southern zone related to volcanic rocks
moderately to highly differentiated, such as the Santa Rosa dome.
Figure 4.1
Figure 4.2
Figure 4.3
Figure 4.4
Figure 4.5
Batolito Andahuaylas - Yauri
Figure 4.6
1.- Sistemas de Fallas Urcos – Sicuani – Ayaviri
2.- Falla Patamburco.
3.- Falla Puyentimari.
4.- Deflexión de Abancay
Figure 4.7
4.2 GEOCHEMICAL OF STREAM SEDIMENT ANDAHUAYLAS – YAURI BATHOLITH
The geochemical values of the stream sediment samples have allowed to elaborate isovaloric
maps concerning to the Andahuaylas - Yauri Batholith. Knowing the potential of the batholith by
means of the inventory of the mineral deposits has been interpreted the copper, gold,
molybdenum maps isovalóricos (Fig. 4.8, 4.9 y 4.10) with the purpose of correlating the high
concentrations of these chemical elements with the location of the deposits in the Andahuaylas yauri domain of the and to be able to them to correlate with some other areas of interest.
The copper isivaloric map shows a clear tendency of the areas of more concentration with strike
SE - NW coinciding spacely with the Andahuaylas - Yauri Batholith outcrops. These areas of
more concentration involve big groups of deposits as: the Tintaya, Katanga, Las Bambas,and
Cotabambas cluster. But it is also clear that exist a great quantity of small anomalies that
indicate vestiges of some mineral deposit no yet discover.
On the other hand the gold isovaloric map shows a clear tendency in SE - NW strike much more
straight that the Copper tendency. Their geochemical anomalies coincide with important cluster
as Cotabambas where are located the Cu - Au porphyries. This tendency also includes the
Tintaya, Katanga and Bambas cluster. A very important observation with regard to the gold is the
anomaly that form the group of occurrences that are located in the surroundings of Utupara,
Trapiche and Peña Alta. Highlighting that most of the occurrences is related to gold veins in
carbonated rocks, those which at the moment are being worked handmadely. The same as the
copper the study area shows important geochemical anomalies that deserve more studies to the
detail.
The Mo isovaloric map shows a distribution of anomalies completely different to that of the Cu an
Au maps. Their higher values are related to an area among San Diego - Trapiche going by
Utupara until the Cotabambas cluster. We can observe as the Cristo de los Andes - Haquira
ocurrences coincides with the Mo geochemical anomalies. Toward the north of the Katanga
cluster and east of The Bambas Cluster is observed a wide anomalous area to which any
occurrence is not still associated.
The geochemical correlations among the Au - Cu and Mo indicate a better correlation for the Au Cu. The south part of the Andahuylas - Yauri batholith outcrop volcanic rocks moderately
differentiated where until the moment have been dicover important deposits as Azuca, Millo and
Crespo.
In the 3D graph it is observed clearly the anomalies belt that form the Tintaya, Katanga Las
Bambas cluster. This group of deposits belongs to oneself age and they are aligned in sense SE NW, then with these evidences we could infer the possible existence of a regional fault that
controlled the location of these mineral deposits.
Figure 4.8
Figure 4.9
Figure 4.10
Figure 4.11
4.3 GEOCHEMICAL OF STREAM SEDIMENT ON THE COLCA AND JALAOCA ZONES
Product of the combined investigations between INGEMMET and KIGAM some areas were
determined with geologic potential as Jalaoca and Colca. These areas are inside the Batolito
Andahuaylas - Yauri domain
very near some
important deposits as Utupara and the
Cotabambas cluster, respectively.
By means of the stream sediment isovaloric maps stream it is observed that boths areas
regionally are related to anomalous zones (Fig. 4.12, 4.13, 4.13, 4.14, 4.15, 4.16 and 4.17). The
Colca area is inside the influence of the Cu - Au anomalies of the Cotabambas cluster, while the
Jalaoca area is inside the domain of the Au - Cu - Mo anomalies of the deposits of Utupara San Diego and Trapiche..
For a better visualization were made isovaloirc local maps, with smaller quantity of stream
sediment samples and was the expected the isovaloric local maps local are not identically similar
to the regional maps.
On the local isovaloric maps of the Colca area, it is still observed a strong Cu - Au anomaly, while
the molybdenum is only restricted to the highest parts on the Cotabambas cluster. The local
isovaloric maps of Jalaoca show that this area is surrounded by strong Cu - Au and Mo
anomalies, coinciding with the mineralization type of the mineral deposits that surround him.
Both areas are free of mining concessions and the geologic characteristics are very similar to that
of the neighboring deposits. The mineralization evidences in surface check the potential of the
areas.
It should take in consideration that the quantity of samples that define to these areas like
interesting are very little, it is recommended a geochemestry prospecting work very more detail.
Figure 4.12
Figure 4.13
Figure 4.14
Figure 4.15
Figure 4.16
Figure 4.17
5.- ISOTOPIC AND GEOCRHONOLOGY DATA INTERPRETATION IN THE ANDAHUAYLAS YAURI BATHOLITH"
INTRODUCTION
The metallogenetic belt of the Andahuaylas Yauri batholith is characterized mainly by the
occurrence of deposits of type Cu - Mo porphyry and skarn. In smaller measure also there are
other mineralization styles like veins and beds associated to several porphyry systems. This belt
host important deposits and prospect as Tintaya, The Bambas, Antapacay, Los Chancas,
Katanga, Cotabambas, Trapiche, Morosayhuas etc.
The geology is characterized by the occurrence of marine and continental sequences of
Mesozoic and Cenozoic age which were intruyed for a multiphase igneous system (Andahuaylas
- Yauri Batholith) of Eocene - Oligocene age which has evolution mainly from early phases with
presence of gabros, gabrodiorites and diorites, followed by intermediate phases with
monzodiorites and cuarzodiorites to arrive finally to phases more acids in the mineralización
stage with presence of granodiorites and monzonites.
A series of late dikes of varied composition cuts the previous phases indistinctly.
The economic mineralization associated to the deposits of porphyry and skarn type are related to
late Eoceno - Oligocene intrusions (Perello, 2003). it is certain that exist a good quantity of
geochronology data distributed in the Andahuaylas - Yauri batholith, but there are still areas that
not had information of the ages of the different intrusions as well as of the mineral occurrences.
This is evidenced overalls in the northwest sector of the batholith
A good quantity of geochronology data of the main intrusions associated to the main deposits
exists, as well as of the ages of the respective mineralizations. However the information ofPb - Pb
and Sr isotopic data are quite poor. The entirety of analyzed data and interpreted it comes from
samples taken among 2007 2008 by A. Bustamante and M. Mamani. Starting from these data a
series of diagrams has been elaborated to characterize the possible origin of the mineralization
and the relationship that it exists between the ores and the host rock. This information was
upgraded and reinterpreted starting from the new data that are come obtaining in the field.
Likewise, INGEMMET inside the mark of the international project with the Geologic Service of
South Korea (KIGAM), during the 2010 it developed an isotopic - geochronology investigation
project in the Batolito Andahuaylas - Yauri batholith, highlight the Cotabambas cluster.
The main objective of this investigation is to know the temporary relationship among the
porphyries that conform the Cotabambas cluster by means of Ar-Ar datation and also to
determine its mineralization source by means of Pb - Pb and Rb - Sr radiogenic isotopes. Then
this information will serve like base to know the possible potential of some other prospects take
the premise: "If isotopic signature of well - know deposits is registered and this it is similar with
that of some prospects that is inside the same geologic enviroment, this last has a great potential,
due that maybe the mineralization processes have been the same".
Isotopic database of the study area is scarce and it includes 06 samples of Pb - Pb isotopes and
02 samples of Rb/Sr taken 2008 for Bustamante, A. and 02 samples of sulfides taken by
Mamani, M.
The information of ages of the different phases of the Andahuaylas - Yauri Batholith has been
analyzed from published data in the database of INGEMMET. This information includes a total of
60 samples inside the study area.
To this information sum a new database from the international cooperation among INGEMMET
and KIGAM that it includes 2 datation Ar-Ar, 4 datation Rb-Sr and 4 Pb - Pb isotopes. This
investigation was carried out exclusively in the Cotabambas cluster that involves the Azullccaca,
Huaclle, Ccalla and Ccarayoc porphyry deposits.
5.1 Interpretation of isotope data
Cotabambas Cluster
During 2010 KIGAM and INGEMMET realized evaluation studies of economic potential of
the Andahuaylas – Yauri Batholith. During the first field trip (March), some samples were
collected for isotopic studies of the main porphyry centers of Cotabambas cluster (Tabla
5.1). The sampling methodology for Pb-Pb isotope studies was to identify in the core
drilling the areas of potassic alteration of the main possible porphyry or mineralizing and
sequentially identify all the different types of characteristics veins of the porphyry with
areas of highest law of Cu - Au. The veins of most interest to this isotopic study were the
type B veins (veins of quartz with a central suture of sulphides) within which the separate
mineral for the four porphyry centers was pyrite.
he geological description of the type B veins in the porphyry of this cluster would be
summarized as centimetric quartz veins, irregular, with a central suture filled by pyrite
and chalcopyrite within a zone of potassic alteration, note the average pink color rock
surrounding the veins (potassium feldspar).
The separation of minerals was done manually at the INGEMMET, using a binocular
microscope Olympus model. The samples were labeled and sent to the Geological
Survey of South Korea (KIGAM) for their isotopic analysis.
Potassic alteration
Tipe B vein
Potassic alteration
Photo N° 5.1.- Type B vein, with a central suture of sulfides (pyrite and
chalcopyrite, notice the potassic alteration.
Type B vein
Potassic alteration
Photo N° 5.2.- Type B vein within the potassic alteration
(Cotabambas cluster)
Type B vein
Potassic alteration
Photo N° 5.3.- Type B vein within potassic alteration, notice the
central suture of pyrite and chalcopyrite (Cotabambas cluster)
Type B vein
Potassic
alteration
Type M vein
(magnetite)
Photo N° 5.4.- Type B and M veins with potassic
alteration of the main porphyry
Fresh rock with
porphyritic texture
(Cotabambas cluster)
Foto N° 5.5.- Porphyritic texture of the fresh rock of the
Cotabamabas cluster.
Ar-Ar geochronological studies had a very similar methodology. It identified the "main
porphyry" within each ones porphyries of Cotabambas cluster. The studies focused on
the potassic alteration, trying to identify the type EB veins (early biotite), with the purpose
of dating the hydrothermal biotite, a product of hydrothermal alteration of the main
porphyry.
The EB type veins were almost absent from drill cores and if present were millimeter very
difficult to separate for geochronological studies. In this way only could separate the
biotite of the Ccalla and Azullccaca porphyries. Biotites were forming small grains and
were related to potassic alteration where the main veins were type "B" and "M".
These biotites were separated manually at the INGEMMET laboratories using a binocular
microscope, and then be labeled and sent to the Geological Survey of Korea (KIGAM) for
geochronological studies.
Hydrothermal Biotite
Foto N° 5.6.- Hydrothermal biotite in small grains associated
with potassic alteration and type B veins (Azullccaca Porphyry).
Isotopic studies of Rb-Sr, followed a similar methodology of the geochronological studies
mentioned above. Hydrothermal alterations were identified in the cores, but this time we
focus on phyllic alteration (quartz - sericite). The objective of this sampling was to identify
the sericite and chlorite, in order to obtain a sample rich in sericite and other poor in
sericite, in order to correct the excess of the first sample and be able to realize isotopic
studies.
Phyllic altreration was not very good development. It was decided not to try to separate
crystals of sericite (model age), but work through total rock (isochronous age). We
collected a total of 8 samples, two samples per each porphyritic deposit, a sample rich
and another poor of sericite, in order to obtain a corrected line of the isotope
interpretations.
Las muestras fueron además evaluadas mediante el PIMA, el cual descartó algunas
muestras erróneas, donde se había confundido la clorita con la illita, la cual es muy
similar pero de aspecto más jabonoso.
The samples were also evaluated using the PIMA, which ruled out some wrong samples,
which had confused the chlorite to illite, which is very similar but soapy looking.
Illita
Photo N° 5.7.- Disregarded sample for isotopic studies where it is observed illite minerals,
who had been confused by the chlorite. (Ccarayoc Porphyry).
Photo N° 5.8.- Samples with chlorite (Azullccaca Porphyry)
Photo N° 5.9.- Sericite (Huaclle Porphyry)
Table 5.1 Samples list for isotopic and geochronology studies in the Cotabambas cluster.
ISOTOPIC STUDY IN PROYECT INGEMMET - KIGAM
IDEM
1
2
SAMPLE
Kigam-2010-020
Kigam-2010-010
DEPOSIT
Ccalla Porphyry (Au - Cu)
Azullccaca Porphyry (Au-Cu)
Cluster
Cotabambas
Cotabambas
MINERAL STUDY
Biotite
Biotite
METHOD
Ar - Ar
Ar - Ar
Geochronology
Geochronology
Observation
separated sample
separated sample
3
4
5
6
7
8
9
10
Kigam-2010-011
Kigam-2010-012
Kigam-2010-016
Kigam-2010-017
Kigam-2010-003
Kigam-2010-002
Kigam-2010-008
Kigam-2010-007
Azullccaca Porphyry (Au-Cu)
Azullccaca Porphyry (Au-Cu)
Ccalla Porphyry (Au-Cu)
Ccalla Porphyry (Au-Cu)
Huaclle Porphyry (Au-Cu)
Huaclle Porphyry (Au-Cu)
Ccarayoc Porphyry (Au-Cu)
Ccarayoc Porphyry (Au-Cu)
Cotabambas
Cotabambas
Cotabambas
Cotabambas
Cotabambas
Cotabambas
Cotabambas
Cotabambas
Clorite
Sericite
Clorite
Sericite
Clorite
Sericite
Clorite
Sericite
Rb-Sr
Rb-Sr
Rb-Sr
Rb-Sr
Rb-Sr
Rb-Sr
Rb-Sr
Rb-Sr
Geochronology
Geochronology
Geochronology
Geochronology
Geochronology
Geochronology
Geochronology
Geochronology
whole rock
whole rock
whole rock
whole rock
whole rock
whole rock
whole rock
whole rock
11
12
13
14
Kigam-2010-023
Kigam-2010-004
Kigam-2010-013
Kigam-2010-005
Ccalla Porphyry (Au - Cu)
Huaclle Porphyry (Au -.Cu)
Azullccaca Porphyry (Au-Cu)
Ccarayoc Porphyry (Au-Cu)
Cotabambas
Cotabambas
Cotabambas
Cotabambas
Pyrite
Pyrite
Pyrite
Pyrite
Pb-Pb
Pb-Pb
Pb-Pb
Pb-Pb
Isotopic Geochemistry
Isotopic Geochemistry
Isotopic Geochemistry
Isotopic Geochemistry
separated sample
separated sample
separated sample
*no separated sample
*the Kigam-2010-005 it is impossible to separate because the mineralización is very fine, but is possible separate for dense fluids and can to be study for pyrite o calcopyrite.
04-May-10
The interpretation of isotope data was made from 10 samples divided into 08 samples
from ore sulphide (pyrite and galena) and 02 samples belonging to the host rock (Table
5.2).
Table 5.2 Pb isotopic results of NW Andahuaylas-Yauri Batholith
Samples
LONG
LAT
206Pb/
Material 204Pb
Error
%
207Pb/
204Pb
Erro r
%
208Pb/
204Pb
Error
%
Author
UTU-001
-72.816
-14.352 Pirita
18.596
0.041
15.629
0.044
38.661
0.044 Bustamante., 2008
UTU-002
-72.802
-14.349 Pirita
18.645
0.007
15.652
0.010
38.760
0.010 Bustamante., 2008
UTU-003
-72.815
-14.354 Pirita
18.641
0.020
15.654
0.019
38.732
0.023 Bustamante., 2008
UTU-004
-72.815
-14.349 Pirita
18.675
1.055
15.729
1.061
38.963
1.065 Bustamante., 2008
UTU-005
-72.815
-14.354 Pirita
18.703
0.009
15.662
0.009
38.790
0.009 Bustamante., 2008
UTU-013
-72.833
-14.366 Pirita
18.492
0.007
15.633
0.006
38.595
0.007 Bustamante., 2008
UTU-012
-72.815
-14.349 Diorita
18.848
0.008
15.649
0.008
38.941
0.008 Bustamante., 2008
UTU-016
-72.815
-14.351 Diorita
18.755
0.007
15.638
0.008
38.839
0.008 Bustamante., 2008
CH-4
-72.660
-14.181 galena
18.915
-
15.665
-
38.632
-
Mamani et al., 2008
LG-16
-72.660
-14.181 galena
18.724
-
15.647
-
-
-
Mamani et al., 2009
As mentioned the Pb isotopic data of the study area is still quite poor however has made
a preliminary interpretation of the samples of ore (sulphide) and host rock with existing
data of the samples located in the NW sector of the belt. To characterize the possible
sources of metals has been worked using Plumbotectónico and Toriogenico diagrams.
Figure 5.1: Comparison of ranges of isotopic ratios of
208
Pb/204Pb of mineralization and host rock.
206
Pb/204Pb,
207
Pb/204Pb and
In Figure 5.1 may provide that in general the values of the isotopic ratios of 206Pb/204Pb
are somewhat greater in the host rock (diorite) than in the samples of ore (sulphide). This
is because in general the rocks (diorite) store more uranium in their composition than the
sulphides, in this case pyrite and galena.
Then the isotopic values of the rocks are more radiogenic than the values of the ore due
to show the evolution of uranium from the time of its formation until today. The opposite
occurs with ore samples showing the initial isotopic composition of lead and that the
sulfides generally do not have uranium within its crystal lattice.
The sulfides show a wide variation and even more radiogenic than the host rock with
respect to the isotopic ratios of 208Pb/204Pb and 207Pb/204Pb. This variation would indicate
that fluids had contamination crustal subordinate of oldest rocks (greater enrichment
relative to 207Pb to 206Pb) and probably with reason Th / Pb than the average upper crust.
Analysis of the diagrams
207Pb/204Pb
vs 206Pb/204Pb and
208Pb/204Pb
vs 206Pb/204Pb
In the diagram 207Pb/204Pb vs 206Pb/204Pb established for Uranogénico Plumbotectónico
model (Figure 5.2) we can see that most mineralized samples (pyrite and galena) and
host rocks (diorite) are located between the curve of upper crust and orogenic mixture
curve which suggests that the main source of metals are upper crustal rocks.As the most
sulphides points follow the same trend of Pb isotopic evolution curve of the host intrusive
rocks, may be admitted to these rocks as the Pb main source of the ore minerals.In the
diagram
208Pb/204Pb
vs
206Pb/204Pb
established for the Toriogénico model (Figure 5.3)
you can see that the source has a ratio Th / Pb above average but did not become
elevated. Apparently the lead is not from mantle because if so the values would be below
the orogen curve.Most samples of ore show isotope compositions of
207Pb/204Pb
y
206Pb/204Pb
208Pb/204Pb,
homogeneous suggesting that the main source of metals
mineralization would be intrusive complexes themselves and this would result from a fluid
flow within the host rocks.
16
207
204
Pb/
Pb
15.8
Corteza
superior
Orogeno
15.6
Manto
15.4
Corteza
Inferior
15.2
Sulfuros
Diorita
15
15
16
17
18
19
206
204
Pb/
Pb
20
Figure 5.2: Isotope compositions diagram of 207Pb/204Pb vs 206Pb/204Pb for samples of ore and
fresh rock at NW area of Andahuaylas-Yauri Batholith. It was used as reference curves of Pb isotopic
evolution established for the Plumbotectónico-Uranogénico model of Zartman & Doe (1981).
C
39
208
B
204
Pb/
Pb
38.8
D
38.6
38.4
38.2
38
37.8
A
37.6
37.4
Sulfuros
Diorita
37.2
37
16
17
18
19
206
204
Pb/
Pb
20
Figure 5.3: Isotope compositions Diagram of 208Pb/204Pb vs 206Pb/204Pb for samples of ore and
fresh rock at NW area of Andahuaylas-Yauri Batholith. It was used as reference curves of Pb isotopic
evolution established for Plumbotectónico-Toriogénico model of Zartman & Doe (1981).
5.2 Location of the study area within the Pb isotopic provinces in the Andes
(Macferlane et al., 1990)
The isotopic values of lead (isotopic signatures) of the rocks and their ore located along
the Andes of South America vary in direct proportion to their distance to the Peru-Chile
Trench. The Peru-Chile Trench marks the geological boundary between the Nazca Plate
to the west to form the south-eastern ocean floor of Pacific Ocean and the South
American plate to the east. As is known the convergence of these two plates produces a
subduction of the Nazca plate (with sediment cover) in the South American continent
generating the fusion of mantle beneath the western edge of South America. Magmas
resulting from this fusion emerge producing an interaction with the continental crust; this
interaction is manifested in a long history of volcanic activity and generation of associated
mineral deposits. Ore formation by subduction along the Peru-Chile Trench has produced
significant variations in lead isotope ratios for the different andean deposits. Lead isotopic
ratios vary with the distance to the fossa but also vary because of differences in the
geology of the South American crust. In general, these isotopic variations reflect the
growth of Pb radiogenic in the South American continental crust with respect to the
distance to the Peru-Chile Fossa (Macferlane et al., 2005).
The Andes are divided into three fundamental isotope provinces of lead (Macferlane et
al., 1990) in these you can see the existence of a parallel to the Peru-Chile Fossa (Fig.
5.4). The isotopic signatures vary from west to east, from the isotopic I province to the
isotopic III province, according to its distance to the fossa.
In the isotope compositions diagram of 207Pb/204Pb vs 206Pb/204Pb (Figure 5.4) we
can see that both samples of ore (pyrite and galena) and the rocks of the study area are
mostly located close to the zone of Province II confirming its geographic location within of
this province as shown on the map. In the Uranogénico diagram (Fig. 5.4) samples away
somewhat from the zone of Province II should however consider that these boundaries
between provinces are not rigid and there may be an overlap between them (Macfarlane
et al., 2005).
Figure 5.4: Map Pb isotopic provinces of the Central Andes and Thorogénicos diagrams (A) and
Uranogénico (B) containing samples of ore and rock in the NW sector of the Andahuaylas – Yauri
Batholith (Modified from Macfarlane et al., 1990 by Tosdal et al., 1999).
5.3 Comparisons of Pb isotopic compositions of some deposits in Peru.
For comparative purposes have been plotting the values of Pb isotopic ratios of some
typical Peruvian deposits trying to include the main mineralized belts of Peru (Figure 5.5).
It can see that there is a lead radiogenic evolution with values of isotopic composition that
increase from deposits near the subduction zone to the farthest.Paleocene porphyry
deposits in southern Peru (Toquepala and Cerro Verde) have Pb isotopic compositions
less radiogenic and San Vicente Mississippi Valley deposit the more radiogenic values.
This feature is typical of these deposits because occurs a movement of fluids through
sedimentary rocks, but this may also suggest that there is an increase in these isotopic
ratios with respect to the distance to the Peru-Chile Trench (Macferlane et al., 2005).
Orcopampa samples demonstrate isotopic ratios with values close to those of the
Andahuaylas – Yauri Batholith. Yanacocha and Julcani show outliers with a mayor range
of isotopic composition characteristic of epithermal deposits. Miocene porphyries in
northern Peru (Galeno and Michiquillay) have values somewhat higher than the ores of
the Andahuaylas - Yauri Batholith but overall seem to express predominantly orogenic
material.
Figure 5.5: Comparison of Pb isotopic ratios of some samples of ore from Andahuaylas - Yauri Batholith
with other peruvian deposits. 207Pb/204Pb vs 206Pb/204Pb diagram showing Pb isotopic comparison of
different deposits.
5.4 Interpretation of Sr Isotopes
To perform a preliminary characterization of metal sources in mineralization
was analyzed two samples taken at the Utupara prospect in 2008. The rocks
were taken considering the hydrothermal alteration of the main phase of Utupara
porphyritic complex, so that the results should refer to the initial isotopic
composition of the mineralizing fluid resulting from the interaction with the host
rock (see Table 5.3).
Table 5.3: Results about 87Rb/86Sr and 87Sr/86Sr relation in the NW sector of the
Andahuaylas-Yauri Batholith (Utupara prospect).
No. Campo
Material
Rb(ppm)
Sr(ppm)
Rb /Sr (X)
87
86
Error
Sr /Sr (Y)
87
86
Error
UTU-007 D84
Diorite
57.3
332.4
0.499
0.014
0.706526
0.000056
UTU-008 D84
Diorite
164.43
1116.29
0.4262
0.0034
0.70585
0.00005
The strontium isotopes are used as an indicator of the potential size of porphyry deposits
(Tassinari, 2007). If we assume that in general all porphyries are formed by the same
process with a variation of the energy of the fluid can then be deduced that those fluids
that have a high energy, a strong heat source, used a relatively short time during the
ascent process to through the crust indicating they will not have significant crustal
contamination and hydrothermal circulation will be in a much larger area. This is
manifested by low values in the initial ratio of Sr87/Sr86 (> 0706). If the fluids have a low
energy these go through the crust in a longer period to have enough time to suffer a
crustal contamination which is manifested in high values of the initial ratio of Sr87/Sr86
(<0.706) (Tassinari, 2007).
From these relations we can deduce that if the porphyry have low initial Sr isotope ratio
then has a chance to be a large deposit, if the ratio is high, indicating strong crustal
contamination, then there is likely to be small.
The initial strontium isotope ratios for Utupara (0.7065 to 0.7058) are very similar to those
of Cº Romero porphyry (0.7063) and Copaquire (0.7058) respectively. For this reason
allow to interpret (Figure 5.6) that Utupara prospect has a potential to be a small to
medium porphyritic deposit.
Figure 5.6: Comparison of age, initial isotopic ratios of Sr87/Sr86 and tonnages of different Porphyry
deposits of Chile. (Courtesy of F. Munizaga in Tassinari, 2006)
6. - Conclusion

Andahuaylas - Yauri Batholith presents very interesting areas for the geologic
exploration, but the topography and the lack of accessibility hinder the work.

Jalaoca area is very interesting, This area present geologic evidences that are
characteristic of the porphyry deposits, It is necessary more studies to the detail.

Colca area is very interesting, it presents very similar geologic characteristic to
the porphyry deposits (Cotabambas cluster), but it is necessary even more
exploration work.

Suparaura area is very similar to the red beds of the Group San Jerónimo Group,
but the potential of the Suparaura area seems to be minimum.

The structural control in the study area is very complex and this dominated by
compressive stress that acted in different senses.

The field trip to the study area allowed to recognize the following types of
deposits: Porphyries (Cu - Au - Mo), Skarn, Au and polimetalic - veins and
copper sulfides in red beds. The gold mineralization can be disseminated in
porphyries (0.4 g/tn) or host in veins with a grade that reaches 7 gr/tn.

The correlative studies of initial strontium isotopes indicate up to now that the
potential of porphyries it is medium to small. (<100, 000 Tn)

The 3D isovaloric maps show a geochemical anomalies belt that should be
studied much more to the detail

The social problems are a factor that should work with much care, to carry out
the exploration works.

The Jalaoca, Colca and Suparaura areas at the moment are in process for
ANAPs.